Carrier heads, planarizing machines and methods for mechanical or chemical-mechanical planarization of microelectronic-device substrate assemblies

ABSTRACT

Planarizing machines, carrier heads for planarizing machines and methods for planarizing microelectronic-device substrate assemblies in mechanical or chemical-mechanical planarizing processes. In one embodiment of the invention, a carrier head includes a backing plate, a bladder attached to the backing plate, and a retaining ring extending around the backing plate. The backing plate has a perimeter edge, a first surface, and a second surface opposite the first surface. The second surface of the backing plate can have a perimeter region extending inwardly from the perimeter edge and an interior region extending inwardly from the perimeter region. The perimeter region, for example, can have a curved section extending inwardly from the perimeter edge of the backing plate or from a flat rim at the perimeter edge. The curved section can curve toward and/or away from the first surface to influence the edge pressure exerted against the substrate assembly during planarization. The second surface of the backing plate is a fixed, permanent surface. The backing plate can further include a permanent, low-friction coating over at least a portion of the perimeter region. The bladder is configured to extend over the second surface of the backing plate to form a fluid cell between the bladder and the second surface.

TECHNICAL FIELD

[0001] The present invention relates to carrier heads and methods forforming planar surfaces on microelectronic-device substrate assembliesin mechanical or chemical-mechanical planarizing processes.

BACKGROUND OF THE INVENTION

[0002] Mechanical and chemical-mechanical planarizing processes(collectively “CMP”) are used in the manufacturing of microelectronicdevices for forming flat surfaces on semiconductor wafers, fieldemission displays and other types of microelectronic-device substrateassemblies. FIG. 1 schematically illustrates a portion of an existingplanarizing machine 10 having a rotating platen 20, a carrier assembly30 and a polishing pad 50. An under-pad 25 can be attached to an uppersurface 22 of the platen 20 for supporting the polishing pad 50. In manyplanarizing machines, a drive assembly 26 rotates (arrow A) and/orreciprocates (arrow B) the platen 20 to move the polishing pad 50 duringplanarization. In other planarizing machines, such as web-formatplanarizing machines, the platen 20 remains stationary duringplanarization and the carrier assembly 30 moves a substrate assembly 12across the polishing pad 50.

[0003] The carrier assembly 30 controls and protects the substrateassembly 12 during planarization. The carrier assembly 30 typically hasa drive assembly, a driveshaft 31 coupled to the drive assembly, and acarrier head 33 coupled to the driveshaft 31. The drive assemblytypically rotates and/or translates the carrier head 33 to move thesubstrate assembly 12 across the polishing pad 50 in a linear, orbitaland/or rotational motion.

[0004] The particular carrier head 33 illustrated in FIG. 1 ismanufactured by Applied Materials Corporation. This carrier headincludes an external housing 34, a backing plate 40 fixedly attached tothe driveshaft 31, and a bladder 46 attached to the backing plate 40.The housing 34 has a support member 35 and a retaining ring 37 dependingfrom the support member 35. A smooth-walled portion of the driveshaft 31is received in a hole 36 through the support member 35 so that thedriveshaft 31 can rotate independently from the housing 34.

[0005] The backing plate 40 of the carrier head 33 includes an annularrim 41 having an inner surface 42 extending around the perimeter of therim 41. The inner surface 42 is a straight, vertical wall extendingupwardly from the rim 41. The backing plate 40 also includes adisposable pad 43 adhered to the annular rim 41. The disposable pad 43is shaped to have a flat interior portion 44 and a curved perimeterportion 45 curving from the interior portion 44 to the rim 41. The pad43 is a thin, low-friction sheet separate from the backing plate 40 thatprevents the bladder 46 from sticking to the backing plate 40 duringplanarization. The backing plate 40 is received in the housing 34, and anumber of inner tubes 49 a and 49 b support the housing 34 over thebacking plate 40. The backing plate 40 accordingly rotates directly withdrive shaft 31 without necessarily rotating with or moving verticallywith the housing 34.

[0006] The bladder 46 is a thin, flexible membrane attached to thebackside or the perimeter edge of the backing plate 40. A fluid conduit47 through the driveshaft 31, the backing plate 40 and the pad 43couples a fluid supply (not shown) with a cell 48 between the bladder 46and the pad 43. The fluid supply can drive fluid into the cell 48 toinflate the bladder 46, or the fluid supply can withdraw fluid from thecell 48 to deflate the bladder 46.

[0007] To planarize the substrate assembly 12, the carrier head 33retains the substrate assembly 12 on a planarizing surface 52 of thepolishing pad 50 in the presence of a planarizing fluid 60. The bladder46 inflates to exert a desired downforce against the substrate assembly12, and the carrier head 33 moves and/or rotates the substrate assembly12. As the substrate assembly 12 moves across the planarizing surface52, abrasive particles and/or chemicals in either the polishing pad 50or the planarizing solution 60 remove material from the surface of thesubstrate assembly 12.

[0008] CMP processes must consistently and accurately produce auniformly planar surface on the substrate assembly to enable precisefabrication of circuits and photo-patterns. One aspect of formingcomponents on semiconductor or other microelectronic-device substrateassemblies is photo-patterning designs to within tolerances as small asapproximately 0.1 μm. Many semiconductor fabrication processes, however,create highly topographic surfaces with large “step heights” thatsignificantly increase the difficulty of forming sub-micron features orphoto-patterns to within such small tolerances. Thus, CMP processes areoften used to transform a topographical substrate surface into a highlyuniform, planar substrate surface (e.g., a “blanket surface”).

[0009] In the competitive semiconductor industry, it is also desirableto maximize the throughput of CMP processing by producing a blanketsubstrate surface as quickly as possible without sacrificing theaccuracy of the process. The throughput of CMP processing is a functionof several factors, one of which is the ability to accurately form aflat, planar surface across as much surface area on the substrateassembly as possible. Another factor influencing the throughput of CMPprocessing is the ability to stop planarization at a desired endpoint inthe substrate assembly. In a typical CMP process, the desired endpointis reached when the surface of the substrate is a blanket surface and/orwhen enough material has been removed from the substrate assembly toform discrete components on the substrate assembly (e.g., shallow trenchisolation areas, contacts, damascene lines, etc.). Accurately stoppingCMP processing at a desired endpoint is important for maintaining a highthroughput because an “under-planarized substrate assembly may need tobe re-polished, or an “over-planarized” substrate assembly may bedamaged. Thus, CMP processing should be consistent from one wafer toanother to accurately form a blanket surface at the desired endpoint.

[0010] One drawback of the Applied Materials carrier head 33 shown inFIG. 1 is that the low-friction pad 43 wears out and needs to bereplaced. In a typical application, for example, vertical displacementof the substrate assembly 12 and the backing plate 40 causes the bladder46 to periodically engage the perimeter of the pad 43. The contactbetween the bladder 46 and the pad 43 wears down the perimeter surfaceof the pad 43 to a point at which the pad 43 must be replaced. Replacingthe pad 43, however, is time-consuming because the bladder 46 and thepad 43 must be removed from the backing plate 40. Therefore, the AppliedMaterials carrier head 33 illustrated in FIG. 1 is subject to downtimethat reduces the throughput of CMP processing.

[0011] Another drawback of the carrier head 33 is that it may produceinconsistent, non-planar surface features at the edge of a substrateassembly. The planarity of the substrate assembly is a function of, atleast in part the pressure exerted on the substrate assembly by thebladder 46. The contour of the perimeter region 45 of the low-frictionpad 43 may affect the force exerted on the perimeter of the substrateassembly 12. For example, because the substrate assembly 12 may pressthe bladder 46 against the perimeter region 45 of the pad 43 duringplanarization, the contour of the perimeter region 45 can directlyaffect the force exerted against the perimeter of the substrate assembly12. The shape of the perimeter region 45 of the pad 43, however, may beinconsistent over the life of a single pad 43 or from one pad 43 toanother. One reason that the shape of the pad 43 may change is becausethe perimeter region 45 of the pad 43 compresses after a period of use.Moreover, and even more problematic, the shape of the perimeter region45 may be different from one pad 43 to another because each pad 43 ismanually attached to the backing plate 40. Therefore, theinconsistencies of the pad 43 may produce inconsistent, non-planarsurface features at the edge of the substrate assemblies.

SUMMARY OF THE INVENTION

[0012] The present invention is directed toward planarizing machines,carrier heads for planarizing machines, and methods for planarizingmicroelectronic-device substrate assemblies in mechanical orchemical-mechanical planarizing processes. In one embodiment of theinvention, a carrier head includes a backing plate, a bladder attachedto the backing plate, and a retaining ring extending around the backingplate and the bladder. The backing plate has a perimeter edge, a firstsurface, and a second surface opposite the first surface. The secondsurface of the backing plate can have a perimeter region extendinginwardly from the perimeter edge and an interior region extendinginwardly from the perimeter region. The backing plate can furtherinclude a permanent, low-friction coating over at least a portion of thesecond surface. The bladder is configured to extend over the secondsurface of the backing plate to form a fluid cell between the bladderand the second surface. In operation, a fluid can flow through thebacking plate to inflate/deflate the bladder.

[0013] In another embodiment of the invention, the backing plate has atleast one hole defining a fluid passageway, and the perimeter region ofthe second surface has a fixed curvature. The perimeter region, forexample, can have a rim extending inwardly from the perimeter edge ofthe backing plate and curved section extending inwardly from the rim.The perimeter region can alternatively have only a curved sectionextending inwardly directly from the perimeter edge of the backingplate. The curved section can curve toward and/or away from the firstsurface to influence the edge pressure exerted against the substrateassembly during planarization.

[0014] In operation, the carrier head holds a backside of a substrateassembly against the bladder within the retaining ring. The carrier headthen places the substrate assembly on a planarizing surface of apolishing pad and inflates the bladder to exert a desired down forceagainst the substrate assembly. The carrier head also translates thesubstrate assembly across the planarizing surface to remove materialfrom the front side of the substrate assembly.

BRIEF DESCRIPTION OF THE DRAWINGS

[0015]FIG. 1 is a schematic cross-sectional view of a carrier head for aplanarizing machine in accordance with the prior art.

[0016]FIG. 2 is a schematic cross-sectional view of a carrier head for aplanarizing machine in accordance with one embodiment of the invention.

[0017]FIG. 3 is a partial cross-sectional view of a backing plate for acarrier head in accordance with one embodiment of the invention.

[0018]FIG. 4 is a partial cross-sectional view of another backing platefor a carrier head in accordance with another embodiment of theinvention.

[0019]FIG. 5 is a graph illustrating the thickness of substrateassemblies with respect to the radial position across the substrateassemblies for substrate assemblies planarized with different backingplates.

DETAILED DESCRIPTION OF THE INVENTION

[0020] The present invention is directed toward methods and apparatusesfor mechanical and/or chemical-mechanical planarization ofmicroelectronic-device substrate assemblies. Many specific details ofcertain embodiments of the invention are set forth in FIGS. 2-5 and thefollowing description to provide a thorough understanding of suchembodiments. One skilled in the art, however, will understand that thepresent invention may have additional embodiments, or that certainembodiments of the invention may be practiced without several of thedetails described in the following description.

[0021]FIG. 2 is a schematic cross-sectional view partially illustratinga planarizing machine 110 including a carrier assembly 130 having adrive assembly 132 and a carrier head 140 in accordance with oneembodiment of the invention. The drive assembly 132 can have an arm organtry (not shown) with a plurality of actuators (not shown) to move thecarrier head 140 vertically (arrow V), horizontally (arrow H), and/orrotationally (arrow R). The drive assembly 132 has a driveshaft 134including a conduit 135 coupled to a pump (not shown), such as a dualdirection pump to drive a fluid (e.g., air or water) through the conduit135. Suitable drive assemblies for operating the carrier head 140 aremanufactured by EDC Obsidian Corporation, Westech Corporation,Strasbaugh Corporation and Applied Materials Corporation.

[0022] The carrier head 140 of this embodiment includes a housing 150coupled to the drive shaft 134, a cover plate 160 connected to thedriveshaft 134, and a backing plate 170 attached to the cover plate 160.The carrier head 140 can also include a bladder or flexible membrane 190attached to the backing plate 170. As described in more detail below,the carrier head 140 moves a substrate assembly 12 across theplanarizing surface 52 of the polishing pad 50.

[0023] The housing 150 of this embodiment includes a support member 152and a retaining ring 156 depending from the support member 152. Thesupport member 152 can be a circular plate with a hole 154 to receivethe driveshaft 134 so that the shaft 134 can rotate independently fromthe housing 150. Additionally, the hole 154 in the support member 152allows vertical displacement between the cover plate 160/backing plate170 assembly and the housing 150. In one embodiment, a bushing (notshown) can couple the support member 152 to the drive shaft 134 to allowthe drive shaft 134 to rotate freely with respect to the housing 150.The support member 152 can alternatively be a bar extending over thecover plate 160. The retaining ring 156 can accordingly extenddownwardly from either a plate-type or bar-type support member 152 tosurround the cover plate 160, the backing plate 170, and the substrateassembly 12. The housing 150 is spaced apart from the cover plate by anumber of inner tubes 158 a and 158 b, or another type of resilient andcompressible spacer.

[0024] The cover plate 160 is an optional component of the carrier head140. In this embodiment, the cover plate 160 has an annular tongue 162and a hole 164 open to the conduit 135. The hole 164 thus allows a fluidto pass through the cover plate 160. The cover plate 160 is fixedlyattached to the driveshaft 134, and thus rotation of the drive shaft 134directly rotates the cover plate 160. The cover plate 160, for example,can be welded, threaded or otherwise fixedly attached to the drive shaft134.

[0025] The backing plate 170 shown in FIG. 2 is fixedly attached to thecover plate 160 by a number of bolts, screws or other fasteners (notshown). In another embodiment, the backing plate 170 can be attacheddirectly to the drive shaft 134 to eliminate the cover plate 160 fromthe carrier head 140. The backing plate 170 has a first surface 172facing the support member 152, a second surface 174 facing the polishingpad 50, and a perimeter edge 175. The first surface 172 of the backingplate 170 can have a lip 176 extending inwardly from the perimeter edge175 and a depression 177 within the lip 176. The lip 176 can have anannular groove 178 configured to receive the annular tongue 162 of thecover plate 160. The depression 177 in the first surface 172 and thecover plate 160 define a cavity 179 to distribute the fluid from theconduit 135 over the backing plate 170. The second surface 174 of thebacking plate 170 has a perimeter region 182 extending inwardly from theperimeter edge 175 and an interior region 184 extending inwardly fromthe perimeter region 182. The perimeter region 182 can be a planarsection, or the perimeter region 182 can be a curved section that curvestoward or away from the first surface 174 of the backing plate 170. Thebacking plate 170 can further include a plurality of holes 173 to passthe fluid through the backing plate 170.

[0026] The backing plate 170 can be a metal plate composed of aluminum,steel, or another suitable type of metal. The backing plate 170 canalternatively be composed of a hard polymer or other type of hard, rigidmaterial. As such, the perimeter region 182 is a fixed, permanentcomponent of the backing plate 170 that is molded, machined or otherwisefabricated on the second surface 174.

[0027] The second surface 174 of the backing plate 170 is additionallycovered with a permanent, low-friction film or coating 188. Suitablecoating materials include DF-200 manufactured by Rodel Corporation,Teflon® manufactured by E. I. du Pont de Nemours, or other suitablelow-friction or nonstick materials. The coating layer 188, for example,can be deposited onto the second surface 174 in a manner similar tocoating the surface of non-stick cookware. The low-friction coating 188protects the bladder 190 from being damaged during planarizing. Forexample, without the low-friction coating 188, the perimeter of thebladder 190 can be damaged because vertical displacement between thesubstrate assembly 12 and the backing plate 170 can occur to the extentthat the perimeter of the bladder 190 can be compressed between theperimeter region 182 of the backing plate 170 and the substrate assembly12. Additionally, the substrate assembly 12 may flex or bow duringplanarization to the extent that the interior region of the bladder 190can be compressed between the interior region 184 of the backing plate170 and the substrate assembly 12. The low-friction coating 188 protectsthe bladder 190 from tearing or prematurely wearing when it iscompressed between the substrate assembly 12 and the backing plate 170by reducing the coefficient of function across the backing plate 170.

[0028] The bladder 190 can be attached to the backing plate 170 toextend over the second surface 174. In one embodiment, for example, aportion of the bladder 190 can be clamped between the tongue 162 of thecover plate 160 and the groove 178 of the backing plate 170. In anotherembodiment, a clamp-ring (not shown) can clamp the bladder 190 to theperimeter edge 175 of the backing plate 170. The second surface 174 ofthe backing plate 170 and the portion of the bladder 190 extending overthe second surface 174 define a fluid cell 189. In operation, a fluidpasses through the conduit 135, the cavity 179 and the holes 173 toinflate or deflate the bladder 190. As explained in more detail below,the shape of the perimeter region 182 of the second surface 174influences the pressure exerted against the perimeter region of thesubstrate assembly 12 during planarization.

[0029]FIGS. 3 and 4 illustrate various embodiments of the perimeterregion 182 of the backing plate 170 in greater detail. Referring to FIG.3, the perimeter region 182 includes a rim 183 extending inwardly fromthe perimeter edge 175 by a distance “D” and a curved section 185extending inwardly from the rim 183. The interior region 184 of thesecond surface 174 extends inwardly from the curved section 185. Thecurved section 185 of this embodiment curves toward the first surface172 at a radius “r₁” such that the interior region 184 is recessed fromthe rim 183. In one particular embodiment the distance D is 0.122 inchand the radius r₁ is 2.0 inches, and in another embodiment the distanceD is 0.06 inch and the radius r₁ is 3.9 inches. FIG. 4 illustratesanother embodiment in which the perimeter region 182 includes a curvedsection 185 extending inwardly from the perimeter edge 175 and curvingaway from the first surface 174 to the interior region 184. The radiusof curvature “r₂” of the perimeter region 182 shown in FIG. 4 can beapproximately 4.6 inches. In still another embodiment (not shown), theperimeter region 182 is a flat section at the same elevation as theinterior region 184 such that the second surface 174 is planar. As such,the perimeter region 182 can be a curved or flat section that extendsinwardly from either the rim 183 or the perimeter edge 175, and thecurved section 185 can curve either toward or away from the firstsurface 172. Referring to FIGS. 3 and 4 together, the low frictioncoating 188 covers the second surface 174 of the backing plate 170 toprotect the bladder 190 (FIG. 2) from damage during planarization.

[0030] The contour of the perimeter region 182 of the second surface 174influences the pressure exerted by the bladder 190 against the perimeterof the substrate assembly 12. For example, when a significant amount ofvertical displacement occurs between the backing plate 170 and thesubstrate assembly 12 during planarization, the perimeter portion 182 ofthe second surface 174 may directly press an edge portion of the bladder190 against the backside of the substrate assembly 12. The contour ofthe perimeter region 182 of the second surface 174 can accordinglyinfluence the force exerted against the perimeter region of thesubstrate assembly 12.

[0031]FIG. 5 is a graph illustrating the thickness of substrateassemblies with respect to the radial position on the substrateassemblies. Contour line 210, more specifically, illustrates thethickness of a substrate assembly planarized with a carrier head havinga backing plate in which the perimeter region of the second surface hasa rim and a curved section that curves upwardly toward the first surfaceof the backing plate (as shown in FIG. 3). Contour line 220 illustratesthe thickness of a substrate assembly planarized with a carrier headhaving a backing plate in which the curved section curves downwardlyaway from the first surface of the backing plate (as shown in FIG. 4).The radial location and extent that the thickness of the substrateassembly 12 varies at the perimeter edge can thus be partiallycontrolled by the contour of the perimeter region 182 of the secondsurface 174.

[0032] The operation of the carrier head 140 is best illustrated in FIG.2. Before placing the substrate assembly 12 on the polishing pad 50, thecarrier head picks up the substrate assembly 12 by pressing the bladder190 against the backside of the substrate assembly 12 and drawing fluidout of the fluid cell 189. The fluid draws the bladder 190 partiallythrough the holes 173 in the backing plate 170, and the portions of thebladder 190 drawn into the holes 173 create suction points that hold thesubstrate assembly 12 to the bladder. The drive assembly 132 then movesthe carrier head 140 over the polishing pad 50 and lowers the carrierhead 140 until the substrate assembly 12 and/or the retaining ring 156engages the planarizing surface 52. The fluid cell 189 is then filledwith fluid to exert the desired downforce against the substrate assembly12 via the bladder 190. The retaining ring 156 holds the substrateassembly 12 under the bladder 190, and the drive assembly 132 moves thecarrier head 140 and substrate assembly 12 across the polishing pad 50.The relative movement between the substrate assembly 12 and thepolishing pad 50 in the presence of a planarizing solution removesmaterial from the front side of the substrate assembly 12.

[0033] The embodiments of the carrier head 140 shown in FIGS. 2-4 areexpected to reduce the down-time for repairing and maintaining thecarrier head 140 compared to the Applied Materials carrier head shown inFIG. 1. The permanent low-friction coating 188 on the second surface 174of the backing plate 170 protects the bladder 190 from ripping when itcontacts the backing plate 170. The low-friction coating 188 accordinglyeliminates the need for a separate backing pad attached to the backingplate 170 in the carrier head 140. The Applied Materials carrier head,however, requires a separate backing pad 43 (FIG. 1) that wears down andmust be replaced periodically. Thus, unlike the Applied Materialscarrier head, the carrier head 140 does not need to be periodicallydisassembled and reassembled to change out disposable backing pads. Thecarrier head 140 accordingly eliminates a consumable component to reducethe down-time for repairing and maintaining the carrier head.

[0034] Moreover, the embodiments of the carrier head 140 shown in FIGS.2-4 are also expected to produce more consistent planarizing resultsthan the Applied Materials carrier head shown in FIG. 1. Because theperimeter portion 182 of second surface 174 has a permanent, fixedcontour, the backing plate 170 produces a consistent perimeter forcedistribution for a large number of substrate assemblies. The AppliedMaterials carrier head, however, may not produce such a consistentperimeter force distribution because the contour of the backing pad 43(FIG. 1) may change over the life of the pad 43. Moreover, because thebacking pads 43 are manually attached to the Applied Materials carrierhead, the contour of one backing pad 43 may be different than another.Thus, the permanent and fixed perimeter portion 182 of the backing plate170 eliminates a processing variable that can result in inconsistentplanarizing results.

[0035] From the foregoing it will be appreciated that, although specificembodiments of the invention have been described herein for purposes ofillustration, various modifications may be made without deviating fromthe spirit and scope of the invention. The backing plate 170 andlow-friction coating 188, for example, can be composed of materialsdifferent than those disclosed above. Additionally, the perimeter region182 of the backing plate 170 can have additional configurations otherthan those disclosed above, such as compound curve surfaces withmultiple curves. Accordingly, the invention is not limited except as bythe appended claims.

1. A carrier head for mechanical or chemical-mechanical planarization ofa microelectronic-device substrate assembly, comprising: a backing platehaving a first surface, a second surface opposite the first surface, anda low-friction coating permanently affixed to at least a portion of thesecond surface, the second surface having an interior region and aperimeter region, and the perimeter region being a fixed, permanentportion of the backing plate; a bladder extending over the secondsurface of the backing plate to form a fluid cell between the bladderand the second surface, the fluid cell being configured to receive afluid; and a retaining ring extending around the backing plate and thebladder.
 2. The carrier head of claim 1 wherein: the backing platefurther comprises a metal plate having a perimeter edge, a plurality ofholes extending from the first surface to the second surface to providefluid passageways to the fluid cell, and a permanent low-frictioncoating applied to the second surface; the first surface of the backingplate has a lip extending inwardly from the perimeter edge and adepression over the interior region of the second surface; the perimeterregion of the second surface of the backing plate has a flat rimextending inwardly from the perimeter edge of the backing plate and acurved section extending inwardly from the rim, the curved sectioncurving toward the first surface such that the interior region of thesecond surface is recessed from the rim; and the carrier head furthercomprises a cover panel attached to the lip of the first surface todefine a cavity between the depression in the first surface of thebacking plate and the support panel, the cover panel being configured tobe attached to a drive assembly of a planarizing machine.
 3. The carrierhead of claim 1 wherein: the backing plate further comprises an aluminumplate having perimeter edge, a plurality of holes extending from thefirst surface to the second surface to provide fluid passageways to thefluid cell, and a fixed layer of DF-200 covering at least the perimeterregion of the second surface; the first surface of the backing plate hasa lip extending inwardly from the perimeter edge and a depression overthe interior region of the second surface; the perimeter region of thesecond surface of the backing plate has a flat rim extending inwardlyfrom the perimeter edge and a curved section extending inwardly from therim, the curved section curving toward the first surface such that theinterior region of the second surface is recessed from the rim; and thecarrier head further comprises a cover panel attached to the lip of thefirst surface to define a cavity between the depression in the firstsurface of the backing plate and the support panel, the cover panelbeing configured to be attached to a drive assembly of a planarizingmachine.
 4. The carrier head of claim 1 wherein: the backing platefurther comprises an aluminum plate having a perimeter edge, a pluralityof holes extending from the first surface to the second surface toprovide fluid passageways to the fluid cell, and a fixed layer of DF-200covering at least the perimeter region of the second surface; the firstsurface of the backing plate has a lip extending inwardly from theperimeter edge and a depression over the interior region of the secondsurface; the perimeter region of the second surface of the backing platehas a curved section extending inwardly from the perimeter edge andcurving away from the first surface, and the interior region of thesecond surface is a planar section extending inwardly from the curvedsection; and the carrier head further comprises a cover panel attachedto the lip of the first surface to define a cavity between thedepression in the first surface of the backing plate and the supportpanel, the cover panel being configured to be attached to a driveassembly of a planarizing machine.
 5. The carrier head of claim 1wherein the backing plate has a perimeter edge and a curved sectionextending inwardly from the perimeter edge, and the curved sectioncurving toward the first surface such that the interior region of thesecond surface is recessed from the perimeter edge.
 6. The carrier headof claim 1 wherein the backing plate has a perimeter edge, and theperimeter region of the second surface has a flat rim extending inwardlyfrom the perimeter edge and a curved section extending inwardly from therim, the curved section curving toward the first surface such that theinterior region of the second surface is recessed from the rim.
 7. Thecarrier head of claim 1 wherein the backing plate has a perimeter edgeand a curved section extending inwardly from the perimeter edge, and thecurved section curving away from the first surface.
 8. The carrier headof claim 1 wherein the backing plate has a perimeter edge, and theperimeter region of the second surface has a flat rim extending inwardlyfrom the perimeter edge and a curved section extending inwardly from therim, and the curved section curving away from the first surface.
 9. Thecarrier head of claim 1 wherein the permanent low-friction coatingcovers the perimeter region of the second surface of the backing plate.10. The carrier head of claim 1 wherein the low-friction coatingcomprises a film of Teflon permanently attached to the backing plate.11. The carrier head of claim 1 wherein the low-friction coatingcomprises a film of DF-200 permanently attached to the backing plate.12. A carrier head for mechanical or chemical-mechanical planarizationof a microelectronic-device substrate assembly, comprising: an exteriorhousing including a support member and a retaining ring projecting fromthe support member; a backing plate received within the support memberand the retaining ring, the backing plate having a first surface facingthe support member, a second surface facing away from the supportmember, at least one hole through the backing plate to provide a fluidpassageway through the backing plate, and a permanent low-frictioncoating over at least a portion of the second surface, the secondsurface of the backing plate having an interior region and a fixedperimeter region; and a bladder extending over at least the perimeterregion of the second surface of the backing plate, the bladder and thesecond surface defining a fluid cell in which fluid passes though thehole to inflate/deflate the bladder.
 13. The carrier head of claim 12wherein the backing plate has a perimeter edge, and the perimeter regionof the second surface has a curved section extending inwardly from theperimeter edge and curving toward the first surface such that theinterior region of the second surface is recessed from the perimeteredge.
 14. The carrier head of claim 12 wherein the backing plate has aperimeter edge, and the perimeter region of the second surface has aflat rim extending inwardly from the perimeter edge and a curved sectionextending inwardly from the rim and curving toward the first surfacesuch that the interior region of the second surface is recessed from therim.
 15. The carrier head of claim 12 wherein the backing plate has aperimeter edge, and the perimeter region of the second surface has acurved section extending inwardly from the perimeter edge and curvingaway from the first surface.
 16. The carrier head of claim 12 whereinthe backing plate has a perimeter edge, and the perimeter region of thesecond surface has a flat rim extending inwardly from the perimeter edgeand a curved section extending inwardly from the rim and curving awayfrom the first surface.
 17. The carrier head of claim 12 wherein thepermanent low-friction coating covers the perimeter region of the secondsurface of the backing plate.
 18. The carrier head of claim 12 whereinthe low-friction coating comprises a film of Teflon permanently attachedto the backing plate.
 19. The carrier head of claim 12 wherein thelow-friction coating comprises a film of DF-200 permanently attached tothe backing plate.
 20. A carrier head for mechanical orchemical-mechanical planarization of a microelectronic-device substrateassembly, comprising: a flexible membrane; a backing plate having aperimeter edge, a first surface and a second surface opposite the firstsurface, the membrane being attached to the backing plate to extend overthe second surface and define a fluid cell between the bladder and thebacking plate, and the second surface having an interior region and afixed perimeter region configured to impart a desired shape to aperimeter portion of the membrane; and a low-friction coating coveringat least the perimeter region of the second surface of the backingplate.
 21. The carrier head of claim 20 wherein the perimeter region ofthe second surface has a curved section extending inwardly from theperimeter edge and curving toward the first surface such that theinterior region of the second surface is recessed from the perimeteredge.
 22. The carrier head of claim 20 wherein the perimeter region ofthe second surface has a flat rim extending inwardly from the perimeteredge and a curved section extending inwardly from the rim and curvingtoward the first surface such that the interior region of the secondsurface is recessed from the rim.
 23. The carrier head of claim 20wherein the perimeter region of the second surface has a curved sectionextending inwardly from the perimeter edge and curving away from thefirst surface.
 24. The carrier head of claim 20 wherein the perimeterregion of the second surface has a flat rim extending inwardly from theperimeter edge and a curved section extending inwardly from the rim andcurving away from the first surface.
 25. The carrier head of claim 20wherein the permanent low-friction coating covers the perimeter regionof the second surface of the backing plate.
 26. The carrier head ofclaim 20 wherein the low-friction coating comprises a film of Teflonpermanently attached to the backing plate.
 27. The carrier head of claim20 wherein the low-friction coating comprises a film of DF-200permanently attached to the backing plate.
 28. A planarizing machine formechanical or chemical-mechanical planarization ofmicroelectronic-device substrate assemblies, comprising: a supporttable; a polishing pad on the support table, the polishing pad having aplanarizing surface configured to planarize a microelectronic-devicesubstrate assembly; and a carrier assembly having a drive assembly and acarrier head attached to the drive assembly, the drive assembly movingthe carrier head with respect to the polishing pad, and the carrier headincluding a backing plate, a bladder attached to the backing plate, anda retaining ring extending around the backing plate and the bladder, thebacking plate having a perimeter edge, a first surface, and a secondsurface opposite the first surface, the second surface having aninterior region and a perimeter region, and the perimeter region havinga fixed curved section extending toward or away from first surface, andthe bladder being attached to the backing plate to extend over thesecond surface of the backing plate and form a fluid cell between thebladder and the second surface.
 29. The carrier head of claim 28 whereinthe backing plate has a perimeter edge, and the curved section extendsinwardly from the perimeter edge and curves toward the first surfacesuch that the interior region of the second surface is recessed from theperimeter edge.
 30. The carrier head of claim 28 wherein the backingplate has a perimeter edge, and the perimeter region of the secondsurface has a flat rim extending inwardly from the perimeter edge andthe curved section extends inwardly from the rim and curves toward thefirst surface such that the interior region of the second surface isrecessed from the rim.
 31. The carrier head of claim 28 wherein thebacking plate has a perimeter edge, and the curved section extendsinwardly from the perimeter edge and curves away from the first surface.32. The carrier head of claim 28 wherein the backing plate has aperimeter edge, and the perimeter region of the second surface has aflat rim extending inwardly from the perimeter edge and the curvedsection extends inwardly from the rim and curves away from the firstsurface.
 33. The carrier head of claim 28, further comprising apermanent low-friction layer covering at least the perimeter region ofthe second surface of the backing plate.
 34. The carrier head of claim28, further comprising a film of Teflon covering at least a portion ofthe second surface of the backing plate, the Teflon film beingpermanently attached to the backing plate.
 35. The carrier head of claim28, further comprising a film of DF-200 covering at least a portion ofthe second surface of the backing plate, the DF-200 film beingpermanently attached to the backing plate.
 36. A planarizing machine formechanical or chemical-mechanical planarization ofmicroelectronic-device substrate assemblies, comprising: a supporttable; a polishing pad on the support table, the polishing pad having aplanarizing surface configured to planarize a microelectronic-devicesubstrate assembly; and a carrier assembly having a drive assembly and acarrier head attached to the drive assembly, the drive assembly movingthe carrier head with respect to the polishing pad, and the carrier headincluding a flexible membrane and a backing plate attached to theflexible membrane, the backing plate having a perimeter edge, a firstsurface, a second surface opposite the first surface, a permanentlow-friction coating covering at least a portion of the second surface,the membrane extending over the second surface to define a fluid celltherebetween, and the second surface having an interior region and afixed perimeter region configured to impart a desired shape to aperimeter portion of the membrane.
 37. The carrier head of claim 36wherein the perimeter region of the second surface has a flat rimextending inwardly from the perimeter edge and a curved sectionextending inwardly from the rim and curving toward the first surfacesuch that the interior region of the second surface is recessed from therim.
 38. The carrier head of claim 36 wherein the perimeter region ofthe second surface has a curved section extending inwardly from theperimeter edge and curving away from the first surface.
 39. The carrierhead of claim 36 wherein the perimeter region of the second surface hasa flat rim extending inwardly from the perimeter edge and a curvedsection extending inwardly from the rim and curving away from the firstsurface.
 40. The carrier head of claim 36 wherein the permanentlow-friction coating covers the perimeter region of the second surfaceof the backing plate.
 41. The carrier head of claim 36 wherein thepermanent low-friction coating comprises a film of Teflon permanentlyattached to the backing plate.
 42. The carrier head of claim 36 whereinthe permanent low-friction coating comprises a film of DF-200permanently attached to the backing plate.
 43. In mechanical orchemical-mechanical planarization of microelectronic-device substrateassemblies, a method of manufacturing a backing plate for a carrierhead, comprising: constructing a first surface on a plate to be coupledto a drive assembly for the carrier head; forming a second surface onthe plate opposite the first surface to have a perimeter edge, aperimeter region extending inwardly from the perimeter edge and aninterior region extending inwardly from the perimeter region; andcovering at least a portion of the second surface with a permanent filmof low-friction material.
 44. The method of claim 43 wherein forming thesecond surface comprises machining the perimeter region to have a flatrim extending inwardly from the perimeter edge and a curved sectionextending inwardly from the rim and curving toward the first surface.45. The method of claim 43 wherein forming the second surface comprisesmachining the perimeter region to have a flat rim extending inwardlyfrom the perimeter edge and a curved section extending inwardly from therim and curving away from the first surface.
 46. The method of claim 43wherein forming the second surface comprises machining the perimeterregion to have a curved section extending inwardly directly from theperimeter edge and curving toward the first surface.
 47. The method ofclaim 43 wherein forming the second surface comprises machining theperimeter region to have a curved section extending inwardly directlyfrom the perimeter edge and curving away from the first surface.
 48. Themethod of claim 43 wherein covering at least a portion of the secondsurface comprises covering the perimeter region and the interior regionof the second surface with the low-friction film.
 49. The method ofclaim 48 wherein covering at least a portion of the second surfacecomprises coating the second surface with a film of Teflon.
 50. Themethod of claim 48 wherein covering at least a portion of the secondsurface comprises coating the second surface with a film of DF-200. 51.In mechanical or chemical-mechanical planarization ofmicroelectronic-device substrate assemblies, a method of supporting abackside of a microelectronic-device substrate assembly, comprising:expanding a bladder over a fixed, curved perimeter region of a shapingsurface of a backing plate, the curved perimeter region defining a shapeof an edge region of the expanded bladder; and pressing the expandedbladder against the microelectronic-device substrate assembly.
 52. Inmechanical or chemical-mechanical planarization ofmicroelectronic-device substrate assemblies, a method of supporting abackside of a microelectronic-device substrate assembly, comprising:shaping an edge region of a bladder over a solid low-friction perimeterregion of a backing plate having a fixed contour that imparts a desiredshape to the edge region; and pressing the shaped bladder against themicroelectronic-device substrate assembly.
 53. In the fabrication ofmicroelectronic-device substrate assemblies, a method of mechanical orchemical-mechanical planarization of a microelectronic-device substrateassembly, comprising: driving the substrate assembly against aplanarizing surface of a polishing pad by expanding a bladder over afixed, curved perimeter region of a backing plate and pressing theexpanded bladder against the substrate assembly, the curved regionhaving a fixed shaping surface and a low-friction coating to define ashape of an edge region of the bladder; and moving at least one of thesubstrate assembly or the polishing pad with respect to the other toimpart relative motion therebetween and remove material from thesubstrate assembly.